1. Field of the Invention
The subject invention pertains to an improved process for preparing platinum 1,3-diketo compounds in high purity.
2. Background Art
For the production of moldings which are used in the medical sector or come into contact with foods, e.g. baking trays, storage containers, it is necessary to meet demanding purity requirements which are specific in terms of particular impurities.
The catalyst which is used in crosslinking of the moldings which are used in the medical sector or come into contact with foods therefore also has to meet specific purity requirements; in particular, the platinum catalyst has to have a high purity and must not contain any toxicologically unacceptable impurities or by-products and nevertheless has to be able to be produced economically.
It is known from J. Chem. Soc. (1968) 1993-2001 that cylooctadiene-PtCl2 reacts with two molar equivalents of thalium acetylacetonate in chloroform at room temperature to form acacCODPtacac. After stirring, the thalium chloride precipitate is filtered off, the filtrate is evaporated to dryness and the product is obtained by recrystallization from petroleum ether. No information is given about the yield or about the purity of the product.
This literature method is not suitable for a production process since, firstly, the toxic solvent chloroform (risk phrases: 22-38-40, 48/20/22) is used and, secondly, as an even more serious objection, the very toxic compound thalium acetylacetonate (R: 26/28-33-51/53) is used. It is not possible to rule out that residual thalium compounds remain in the product.
J. AM. CHEM. SOC. 92 (1970) 1274-1278 discloses the preparation of 3-(1-acetyl-2-oxopropyl)bicyclo[2.2.1]hept-5-en-2-yl)-(2,4-pentan-edionato-O,O′)platinum from dichloro(endo-bicyclopentadiene)platinum(II), sodium carbonate in a molar excess and acetylacetone in excess. For this purpose, the abovementioned mixture is stirred at room temperature for 4 days. The sodium chloride and sodium carbonate are subsequently filtered off and the filtrate is evaporated to dryness. The resulting product is purified by column chromatography using dichloromethane as eluent and is subsequently recrystallized from dichloromethane. The yield is 55%.
The method has serious disadvantages for a preparation on a production scale, e.g. long reaction times of 4 days and the low yield. In addition, the product has to be purified by column chromatography.